Johnny_B

hello. i need some help, this one has got me stumped. im getting a lean condition (oscillating o2 readings) on bank 1 while bank 2 reads rich at WOT.

background: 2009 4.8 silverado swapped for a '08 6.0L and a 76 mm turbo with LJMS stage 1 turbo cam, 1 walbro 450 pump in tank with stock returnless fuel set up. pushed to 92lb/hr injectors from injector dyamics.
been tuning with HP tuners, my first tune, taking it slow, got a course from the tuning school.
trans - 4l80 swap

tune of idle and part throttle went ok, then upon my first attempt at WOT pull, i got to about 3500 rpm (130kpa boost) and she backfires and spits and goes pop pop pop. (sounds just like that...lol) it wont rev past that point, and as you will see in the log, bank 1 reads lean while bank two is rich, power enrich was set to 10.8. My wideband read all over the map.

I have since sprayed the intake and hoses for leaks with carb cleaner, no change in idle rpm.
I swapped o2 sensors side for side - same lean condition, bank 1.
i pulled the plugs, didnt see much on them as far as indicators of a misfire? but again, im new to this so maybe some of you vets can see what i cant?

any thoughts?ideas? theory's?

il post my log and tune for those interested

Johnny_B

Update.

ive since smoke tested the intake for leaks, none found, I swapped o2 side for side, same consistent lean bank 1 reading. I had my o2 sensors checked for frequency, they were within spec. I swapped out some working coil packs I had, no change. I've tried gapping the plugs (Ngk tr6) at .025 ,.030 , .035. Nothing helped. I've tried going for a 11.5 AFR, thinking maybe just too rich, same issue. I am running out of ideas, anyone have any thoughts??

i also took bank one valve cover off to check for a obviously broken valve spring, they were fine.

Help?
Anyone?

jkwalkercchs

iTrader: (21)

Every get this figured out?

Johnny_B

So little up date, no. It's not fixed. Lol being in Canada I kind of abandoned it once the snow hit and it's been waiting me to tackle it again but, here's what I know and think I know. Upon close inspection of my data logs I found the timing was being pulled back to about 2-3 degrees from the 20 I had commanded this happens consistently everytime the RPM rises above 4000. Consequently that is when bank one (I have a cross over set up for my turbo) begins shortly after with funky lean readings . There's no doubt in my mind with the computer consistently pulling timing at exactly 4000 rpm that there is some kind of rev limiting or safety factor at play.

Why?

So back track a bit - remember I did replace the 4l60 with a rebuilt 4l80 (rebuilt from a very reputable company) who did a conversion from 4x4 to 2wd. Which as you may or may not know involved putting in a reluctor so the speed sensor has something to read.

So when I first started the truck with new trans my speedo was waaaay off , like reading 15 when I'm doing 50 , as a result the computer wasn't hitting it's targets and wasn't shifting properly . Or at all. So I just played with my VSS input in my house tuners until it was close. This allowed me to drive it with reasonable shifts. Now every so often the speedo will randomly loose all Signal and just read 0. If I stop and go again it will pick up signal .

What I think hapoened; put all this together and it seems logical that perhaps there was a mistake and he reluctor wasn't put on? Or it slipped off somehow and is giving faulty readings. I called my trans guy, and he said he is sure he out it on, and was a bit offended i asked. I think the innacuracy of the speedo and altering the VSS may have activated a system to limit the rpm...

So currently I am pondering this... Any thoughts ?? Anything else that could screw the speedo ? Also I removed the VSS sensor and expected to see teeth from the reluctor wheel, which I did not, .I saw smooth machined metal...???

molinafrank2021

I know this is old, but your the only post i can find on the internet with my EXACT issue with my turbo 5.3l....our logs are exactly the same, i cant figure out if its an ignition issue or a fueling issue on mine and im going crazy having to back out of the throttle when she goes lean on bank 1 at 4k rpm. you have steady fuel pressure and your does this, i thought it was my pump pressure causing the issue, but apparently its not with yours. what did you ever come up with? thanks